The present invention relates to a clock signal exracting circuit for extracting and reproducing a clock signal from an inputted data signal, and more particularly to a clock signal extracting circuit for extracting a peak point of the data signal to extract and reproduce a timing clock signal by a waveform portion comparing method in which a pair of finite differences in a waveform are compared with each other.
In conventional clock signal extracting circuits, a fundamental frequency component contained in an input data signal is extracted by making use of, for example, a predetermined characteristic of a low-pass filter or a resonance characteristic of a resonance circuit, and a clock signal is reproduced from the extracted fundamental frequency component.
Such conventional circuits, however, are required to include a number of accurate, stable inductors and capacitors which scarcely degrade with temperature and time, since the low-pass filter or resonance circuit must have a sharp selection characteristic. Further, it is required in the conventional clock signal extracting circuits to be able to adjust the frequency and phase characteristics thereof.
Accordingly, it has been difficult to obtain an economical clock signal extracting circuit. Further, the characteristic of a conventional clock signal extracting circuit has degraded greatly with temperature and time. Furthermore, it has been difficult to fabricate a conventional clock signal extracting circuit in the form of an integrated circuit, since the conventional circuit includes a number of coil parts (namely, inductors).